This invention generally relates to the art of optical fibers and, particularly, to a method and apparatus for cross-connecting the individual optical fibers of a plurality of fiber optic ribbons.
Fiber optic circuitry is increasingly being used in electronics systems where circuit density is ever-increasing and is difficult to provide with known electrically wired circuitry. An optical fiber circuit is formed by a plurality of optical fibers carried by a dielectric, and the ends of the fibers are interconnected to various forms of connectors or other optical transmission devices. A fiber optic circuit may range from a simple cable which includes a plurality of optical fibers surrounded by an outer cladding or tubular dielectric to a more sophisticated optical backplane or flat fiber optic circuit formed by a plurality of optical fibers mounted on a substrate in a given pattern or circuit geometry.
One type of optical fiber circuit is produced in a ribbonized configuration wherein a row of optical fibers are disposed in a side-by-side parallel array and coated with a matrix to hold the fibers in the ribbonized configuration. In the United States, a twelve-fiber ribbon or an eight-fiber ribbon have become fairly standard. In other foreign countries, the standard may range from as a low as four to as high as twenty-four fibers per ribbon. Multi-fiber ribbons and connectors have a wide range of applications in fiber optic communication systems. For instance, optical splitters, optical switches, routers, combiners and other systems have input fiber optic ribbons and output fiber optic ribbons.
With various applications such as those described above, the individual optical fibers of input fiber optic ribbons and output fiber optic ribbons are cross-connected or reorganized whereby the individual optical fibers of a single input ribbon may be separated and reorganized into multiple or different output ribbons. The individual optical fibers are cross-connected or reorganized in what has been called a xe2x80x9cmixing zonexe2x80x9d between the input and output ribbons. The resulting cross-connected input and output ribbons may be terminated to a plurality of fiber optic connectors having ferrules and other fiber-holding components, and the connectors, themselves, are fabricated according to given standards or specifications, e.g., eight-fiber connectors or twelve-fiber connectors. When there are different numbers of input ribbons then there are output ribbons, various problems are created in the connectors, because the connectors are designed to hold and terminate a specific number of fibers. In other words, it would be extremely expensive to maintain an inventory of connectors to accommodate fiber optic ribbons having many different numbers of fibers.
For instance, if a given specification or application requires a single eight-fiber input ribbon and four two-fiber output ribbons, the eight fibers of the single input ribbon must be separated, reorganized and cross-connected so that two fibers from the input ribbon are included in each of the four output ribbons. If it is desirable to use standard eight-fiber connectors in this application, it can be understood that the output connectors terminated to each output ribbon will terminate only two fibers. That means that each eight-fiber connector will have six voids in its ferrule or other fiber holding component. This can create serious problems in actual applications, because in a particular overall circuit scheme it is desirable for the fibers of fiber optic ribbons to be maintained in a given sequence, and it is particularly important that the output fibers be maintained in a given sequence or location emanating from a connector. If an eight-fiber connector terminates only two fibers, six voids remain in the connector which makes it difficult for an operator to properly identify fiber locations. The present invention is directed to solving these problems and to various improvements in the concept of cross-connecting or reorganizing a plurality of fiber optic ribbons.
An object, therefore, of the invention is to provide a new and improved method and apparatus for cross-connecting the individual optical fibers of a plurality of fiber optic ribbons.
In the exemplary embodiment of the invention, a substrate is provided and may have an adhesive thereon to which optical fibers can adhere. A plurality of individual optical fibers are routed onto the substrate to form a plurality of fiber optic input ribbons. The fibers of the input ribbons are reorganized on the substrate to form a plurality of fiber optic output ribbons greater in number than the input ribbons but with lesser number of individual optical fibers than the input ribbons. A plurality of individual dummy optical fibers are routed onto the substrate to increase the number of individual optical fibers of the output ribbons without including the dummy optical fibers in the input ribbons.
It should be understood herein that the terms xe2x80x9cinputxe2x80x9d and xe2x80x9coutputxe2x80x9d are used herein to provide a clear and concise understanding of the invention and, in actual practice, but the number of input ribbons may be greater than the number of output ribbons, but similarly resulting in a discrepancy in the number of fibers between the respective input or output ribbons.
With that understanding, in one embodiment of the invention, at least some of the dummy optical fibers of the output ribbons terminate on the substrate in dead ends. In another embodiment of the invention, at least some of the dummy optical fibers are routed between at least a pair of the output ribbons whereby the dummy optical fibers comprise the fibers of more than one output ribbon.
The input and output ribbons may be coated on the substrate. As disclosed herein, at least some of the input and output ribbons extend beyond a peripheral edge of the substrate. A coating may be applied to the ribbons which extend beyond the edge of the substrate to hold the individual fibers of the ribbons in ribbon form. The extended ribbons may be terminated to a plurality of fiber optic connectors outside the substrate to form an optical fiber cross-connected harness.